how many rounds??

[flatblack]

im pretty new at this, im looking at buying a rifle, not sure if i can afford new yet or not, im looking for a used 243 heavy barrel with a woodstock, im just wondering how many rounds can a rifle fire before it starts to get scary and not worth the money?? also looking for pointers on what to look for what buying a used gun, what kind of questions to ask etc etc... and what should the price range be if its used i dont really want to get ripped off